Lithium ion battery is a chargeable battery which mainly relies on movement of lithium ions between a positive electrode and a negative electrode to achieve charge/discharge. Lithium ion batteries have the advantages of high safety, high voltage and specific energy, long charge/discharge cycle life, etc., thus are widely used in portable electrical appliances such as mobile phone, notebook PC and camera.
Positive electrode material is a core part of a lithium ion battery. The prior art has disclosed a plurality of positive electrode materials for lithium ion battery, such as lithium cobalt oxide, lithium iron phosphate, and lithium manganese oxide, where lithium cobalt oxide has the advantages of high capacity, high voltage, ease of preparation and the like, but cobalt is expensive and harmful to the environment; lithium iron phosphate has the merits of high safety, long cycle life, etc., whereas the electrode made has poor processability and consistency; lithium manganese oxide is a material having three-dimensional lithium ion diffusion channels, and has the advantages of low price, high electric potential, environmental friendliness, high safety, etc., and lithium manganese oxide material is suitable for use in large-scale energy-storage batteries for electric vehicles and the like, thus has become one of the hot research topics. However, the lithium ion batteries using lithium manganese oxide as the positive electrode material has a drawback of poor high-temperature cycling performance which limits further application thereof.
In existing studies, it is generally believed that the specific surface area of lithium manganese oxide is one of the important factors that affect the high-temperature cycling performance of lithium ion batteries, and low specific surface area can reduce contact of lithium manganese oxide with electrolyte solution and thereby reduces dissolution of manganese and improves the high-temperature cycling performance of lithium ion batteries. Currently, lithium manganese oxide material is generally coated with oxide or fluoride or doped with other elements and then sintered at high temperature to obtain lithium manganese oxide having low specific surface area. For example, Chinese patent application publication No. CN1787254 discloses a positive electrode material for lithium ion battery, which is prepared by dissolving a soluble metal salt in a solvent, adding spinel lithium manganate or derivatives thereof to form a suspension, then spray drying the suspension, granulating and calcining to give spinel lithium manganate coated with a metal oxide. Although such coating can improve the high-temperature performance of lithium manganese oxide material to a certain extent, the coating increases steps for producing spinel lithium manganate, and it is difficult to guarantee consistency of the product.
Another Chinese patent application publication No. CN1455466 discloses a spinel lithium manganate with a stable structure which is prepared by calcination of electrolytic manganese dioxide, lithium carbonate, cobalt oxide and a multi-component dopant consisting of nickel, chromium, iron, manganese, selenium and fluorin at a high temperature. This method improves the cycling performance of lithium manganate, but the high-temperature cycling performance thereof is still relatively low. Another Chinese patent application publication No. CN101587950 discloses a lithium manganate consisting of micron-scaled single crystals of regular octahedral shape, which is obtained by ball milling and mixing a composite oxide of manganese and modified metal M and a lithium salt and then calcining. The lithium manganese oxide material obtained by the method has a small specific surface area and an improved high-temperature cycling performance, but poor filling capability.